FBI combs desert terrain for clues in Nancy Guthrie’s disappearance

Detectives are continuing to search for clues related to Nancy Guthrie’s disappearance. (Reuters: Rebecca Noble)

The man detained for questioning in the investigation into the disappearance of Nancy Guthrie, the mother of US show host Savannah Guthrie, has been released.

The suspect was detained hours after the FBI released footage and images from the 84-year-old woman’s porch on the night she went missing.

The video showed a person wearing a ski mask, gloves, a backpack and what appeared to be a gun in a holster.

FBI director Kash Patel said investigators had also spent days trying to recover lost, corrupted, or inaccessible images from the surveillance system.

Even though the images do not show the person’s face, investigators are hopeful someone will know who was on the porch.

FBI agents fanned out across a neighbourhood near Nancy Guthrie’s home and searched through the desert for clues on Wednesday, local time.

Detectives search desert terrain

Several hundred detectives and agents are now assigned to the investigation, which is expanding in the Tucson area, the Pima County Sheriff’s Department said.

A resident said an FBI agent told her they were looking for anything that might have been thrown from a car.

A day earlier, authorities said they had stopped a man near the US-Mexico border.

The man told media outlets early on Wednesday, local time, that he was released after several hours and had nothing to do with Ms Guthrie’s disappearance last week.

Savannah Guthrie has not been on the Today Show since the disappearance of her mother Nancy.   (Supplied: Instagram)

Authorities have not said what led them to stop the man, but confirmed he was released.

The sheriff’s department said deputies and FBI agents also searched a location in Rio Rico, a city south of Tucson, where the man lived.

More than 4,000 calls came into the Pima County sheriff’s tip line within the last 24 hours, the department said on Wednesday afternoon.

Authorities have said for more than a week that they believe Ms Guthrie was taken against her will.

She was last seen at home on January 31 and reported missing the next day.

DNA tests showed blood on her porch was Nancy Guthrie’s, authorities said.

Savannah Guthrie posted the new surveillance images on social media and said the family believed her mother was still alive.

The longtime host of  NBC’s Today program and her two siblings have indicated a willingness to pay a ransom.

It is not known whether ransom notes demanding money with deadlines that have already passed were authentic, or whether the family has had any contact with whoever is responsible.

Authorities have said Nancy Guthrie takes several medications, and there is concern she could die without them.